Q.Name any two physiological barriers that provide innate immunity.
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🔒 Start your 14-day free trial to unlock the full solution →Part (a)Concept understanding — Biology Disease Control
Biology Disease Control — A First Look
Think of your body as a city. Every day, germs (bacteria, viruses, fungi, parasites) try to enter — through the air you breathe, the food you eat, a cut on your skin. Most of the time, your body's defence systems stop them before you even notice. That's immunity, your natural security force.
But sometimes the invaders break through. You get a fever, a cough, an infection. Now you need disease control — the set of actions that stop the illness from spreading and help you recover.
What exactly is disease control?
In biology, disease control means reducing the incidence (new cases), prevalence (total cases), or transmission of a disease. It's not about wiping out every germ — that's impossible. It's about keeping the disease at a level where it no longer threatens public health.
The NCERT textbook divides disease control into two broad approaches:
1. Preventive measures — stopping the disease before it starts
These are actions taken by individuals, communities, and governments to block the entry of pathogens.
- Vaccination — training your immune system to recognise a germ before it attacks. This is the single most powerful tool in disease control.
- Sanitation and hygiene — clean drinking water, proper sewage disposal, handwashing. Many diseases (cholera, typhoid, hepatitis A) spread through contaminated water or food.
- Vector control — killing or avoiding the organisms that carry disease. Mosquito nets, insect repellents, draining stagnant water — these control malaria, dengue, chikungunya.
- Quarantine and isolation — separating sick people from healthy ones during outbreaks. You saw this during COVID-19.
Prevention is always better than cure. Once a disease spreads in a population, controlling it becomes exponentially harder and more expensive. That's why governments invest heavily in vaccination drives and public sanitation.
2. Curative measures — treating the disease once it occurs
Even with the best prevention, some people will fall ill. Curative measures aim to:
- Reduce the severity of the illness (e.g., antibiotics for bacterial infections, antiviral drugs for flu)
- Shorten the duration of the illness
- Prevent complications and death
- Stop the patient from infecting others
The key point: treatment alone cannot control a disease in a population. If you only treat sick people without preventing new infections, the disease keeps circulating.
Why does disease control matter for society?
A single outbreak can paralyse a city. Schools close, hospitals overflow, businesses shut down. The economic cost is enormous. That's why disease control is not just a medical issue — it's a public health issue.
The NCERT textbook emphasises that disease control requires community participation. No matter how good the doctors or vaccines are, if people refuse to vaccinate their children or ignore hygiene, the disease will keep spreading. …
Part (b)Concept understanding — Biofertilizers Biopesticides
Imagine you have a garden. You want your plants to grow strong and healthy, and you also want to keep pests away. There are two main ways to do this: one is with harsh chemicals (chemical fertilizers and pesticides), and the other is with living things or natural substances. Biofertilizers and biopesticides are the second way — they are nature’s own tools for farming.
Let’s start with biofertilizers. Think of them as "living manure." A chemical fertilizer is like giving a plant a direct shot of nutrients — it works fast but can burn the soil over time. A biofertilizer, on the other hand, is a preparation containing live microorganisms (like bacteria, fungi, or algae) that help the plant get nutrients from the soil or air. For example, certain bacteria can take nitrogen from the air and convert it into a form the plant can use. The plant doesn’t get fed directly; instead, the biofertilizer helps the soil become richer and more fertile naturally.
The NCERT textbook (Class 12 Biology, Chapter 10) defines biofertilizers as organisms that enrich the nutrient quality of the soil. The main examples are Rhizobium (a bacterium that lives in root nodules of legumes and fixes nitrogen), Azospirillum and Azotobacter (free-living nitrogen-fixing bacteria), and blue-green algae (like Anabaena) which also fix nitrogen.
Now, biopesticides. These are living organisms or natural substances that control pests — insects, fungi, weeds, etc. — without using synthetic chemicals. Instead of spraying a poison that kills everything (good and bad bugs alike), a biopesticide might use a specific bacterium that only harms a particular caterpillar, or a fungus that attacks a weed. The most famous example is Bacillus thuringiensis (often called Bt), a bacterium that produces a protein toxic to certain insect larvae but harmless to humans, animals, and most other insects.
The key difference between chemical and biological agents: Biofertilizers and biopesticides are renewable, eco-friendly, and do not leave toxic residues in the soil or water. They are a cornerstone of sustainable agriculture — farming that can continue for generations without destroying the land.
Why does this matter for a commerce or humanities student? Because agriculture is not just about biology — it’s about economics, policy, and human health. Chemical fertilizers and pesticides are expensive to produce, can pollute groundwater, and their overuse leads to "superpests" that become resistant. Biofertilizers and biopesticides are often cheaper in the long run, safer for farm workers, and help maintain soil health. Governments around the world (including India) promote them through subsidies and organic farming schemes. Understanding them helps you see why "organic" food costs more, why some farmers switch to natural methods, and how environmental regulations work.
Here’s a quick summary of the main types you should know (from NCERT):
- Biofertilizers:
- Rhizobium (symbiotic with legumes) …
Part (a)
Physiological barriers of innate immunity create body conditions hostile to pathogens. Two examples: acid in the stomach (HCl, low pH) kills ingested microbes, and lysozyme in saliva, tears and other secretions destroys bacterial cell walls. (Body temperature/fever is another acceptable example.) …
Part (a): Two physiological barriers of innate immunity are stomach acid (low pH) and lysozyme in tears/saliva.
Part (b): From the given list, the disease-resistant crop varieties are Himgiri (wheat) and Pusa Komal (cowpea).
Part (a)
Concept-first idea: Innate immunity is the non-specific, present-from-birth defence, and its physiological barriers are internal body conditions that make survival difficult for microbes (distinct from physical barriers like skin).
Two physiological barriers:
- Acid in the stomach (HCl, low pH) — the strongly acidic stomach environment kills most microbes that are swallowed.
- Lysozyme — present in tears, saliva and other secretions, this enzyme digests bacterial cell walls. …
Showing the 12 most recent of 21 on this concept.
- AP EAPCET 2026Set ap-2026-05-19-FN1 markMCQQ.Inactivated whole agent vaccines are used in the treatment of (A) Influenza, Rabies (B) Polio, Typhoid (C) Diphtheria, Tetanus (D) Hepatitis-A, Measles
›Reveal solutionSolution
Inactivated whole-agent (killed) vaccines use the entire dead pathogen;
Influenza and Rabies vaccines are the standard textbook examples. Answer: (A).
Concept and Intuition
Vaccines are classified by what they contain:
- Inactivated (killed) whole-agent vaccines: the entire pathogen, chemically or physically killed so it can't cause disease but still triggers immunity — classic examples are Rabies and Influenza (and Salk/IPV polio).
- Live attenuated vaccines: a weakened but still-living pathogen (e.g. Measles, BCG, oral/Sabin polio).
- Toxoid vaccines: an inactivated bacterial toxin, not the whole organism — e.g. Diphtheria and Tetanus.
Step-by-Step Solution
- Check (A) Influenza, Rabies — both are prepared as killed, whole-pathogen vaccines. Matches "inactivated whole agent" cleanly.
- Check (C) Diphtheria, Tetanus — these are toxoid vaccines (inactivated toxin only, not the whole bacterium), so this doesn't fit "whole agent."
- Check (D) Hepatitis-A (inactivated), Measles (live attenuated) — mixed …
- AP EAPCET 2026Set ap-2026-05-20-AN1 markMCQQ.Assertion (A): Biofertilizers can be used to avoid soil and water pollution Reason (R): By intensive tree plantation nutrients can be recycled (A) Both (A) and (R) are correct and (R) is the correct explanation to (A) (B) Both (A) and (R) are correct but (R) is not correct explanation for (A) (C) (A) is correct (R) is wrong (D) (A) is wrong (R) is correct
›Reveal solutionSolution
Both statements are true, but (R) about tree plantation does not explain the pollution-avoiding action of biofertilizers, so (R) is not the correct explanation.
Concept and Intuition
Assertion: biofertilizers replace or reduce chemical fertilizers, so nutrient run-off and eutrophication (soil and water pollution) are minimised — true. Reason: nutrient recycling through intensive tree plantation (agroforestry) is a genuine ecological benefit, but it concerns plantation ecology, not the mechanism by which biofertilizers reduce pollution.
Step-by-Step Solution
- Evaluate (A): biofertilizers (N-fixers, P-solubilisers, mycorrhizae) lower chemical-fertilizer input ⇒ less pollution. True.
- Evaluate (R): tree plantation can help recycle nutrients through litter fall and decomposition. Broadly true as a standalone statement.
- Test the link: does 'tree plantation recycles nutrients' explain 'biofertilizers avoid pollution'? No — they are unrelated mechanisms.
- Hence both correct, but (R) is not the correct explanation of (A).
Common Mistakes …
- AP EAPCET 2026Set ap-2026-05-20-AN1 markMCQQ.Among the following microbes which is helpful for the absorption of phosphorus from the soil (A) Nostoc (B) Glomus (C) Rhizobium (D) Azospirillum
›Reveal solutionSolution
This tests the mycorrhizal association: Glomus forms VA-mycorrhiza with plant
roots and specifically boosts phosphorus uptake from soil.
Concept and Intuition
Mycorrhiza is a mutualistic symbiosis between fungi and plant roots. The fungus
Glomus forms vesicular-arbuscular mycorrhiza (VAM) — its hyphae penetrate root
cortical cells (forming arbuscules) and also extend well beyond the root's own
absorptive zone into the surrounding soil. Because phosphorus in soil is often
present in forms that diffuse slowly and are depleted right around the root
surface, this greatly extended fungal hyphal network is especially effective at
scavenging phosphate ions from a larger soil volume and delivering them to the
plant, in exchange for photosynthetically fixed sugars.
Step-by-Step Solution
- Consider each option's known ecological role: Nostoc is a nitrogen-fixing cyanobacterium; Glomus is a VA-mycorrhizal fungus; Rhizobium is a nitrogen-fixing bacterium (root nodules of legumes); Azospirillum and Azotobacter are free-living nitrogen-fixing bacteria used as biofertilisers.
- The question specifically asks about phosphorus absorption, not nitrogen fixation. …
- AP EAPCET 2026Set ap-2026-05-20-AN1 markMCQQ.Ringworm is caused by (A) Virus (B) Bacteria (C) Fungi (D) Protozoan
›Reveal solutionSolution
This tests a basic infectious-disease fact: ringworm is a fungal (dermatophyte)
skin infection, not viral, bacterial, or protozoan.
Concept and Intuition
"Ringworm" is a common name for dermatophytosis, a superficial infection of
the skin, hair, or nails caused by a group of keratin-digesting fungi collectively
called dermatophytes (genera Trichophyton, Microsporum, Epidermophyton). The
infection produces the classic dry, scaly, circular ("ring-shaped") lesion with a
raised, active, itchy border — the name comes from the ring-like appearance, not
from any actual worm involvement.
Step-by-Step Solution
- Consider the causative-agent categories: virus, bacteria, fungi, protozoan.
- Recall that dermatophyte infections (ringworm, athlete's foot, jock itch) are specifically caused by a group of fungi adapted to digest keratin in skin, hair, and nails. …
- AP EAPCET 2025Set ap-2025-05-20-AN1 markMCQQ.Match the following List-I: A) Enrich nutrient quality of soil B) Kill insect pest C) Decomposition of dung to produce gas D) Growth of large no. of microbes on Industrial scale List-II: I) Bioreactor II) Biogas III) Bio fertilizes IV) Bio pesticides (A) A-III, B-IV, C-II, D-I (B) A-III, B-II, C-IV, D-I (C) A-III, B-I, C-II, D-IV (D) A-III, B-I, C-IV, D-II
›Reveal solutionSolution
Each biotechnology application is matched to its defining role.
Concept and Intuition
Biofertilizers (like Rhizobium, Azotobacter, mycorrhiza) enrich soil nutrient quality. Biopesticides (like Bt-based products) kill insect pests without synthetic chemicals. Biogas is generated by anaerobic decomposition of dung/organic waste by methanogens. A bioreactor is a vessel used to grow large numbers of cells/microbes on an industrial scale under controlled conditions.
Step-by-Step Solution
- Enrich nutrient quality of soil → Biofertilizers (III).
- Kill insect pest → Biopesticides (IV).
- Decomposition of dung to produce gas → Biogas (II).
- Growth of large numbers of microbes on industrial scale → Bioreactor (I).
- This gives A-III, B-IV, C-II, D-I, matching option (A).
Common Mistakes …
- AP EAPCET 2025Set ap-2025-05-20-FN1 markMCQQ.Select the correct statements among the following I) The use of biofertilizers reduce the use of chemical fertilizers. II) Mycorrhizae enhances phosphorous content in the soil. III) An important biofertilizer in legume crops is Rhizobium. IV) Glomus forms mycorrhizal association with plants. (A) I, II, III (B) II, III (C) III, IV (D) I, III, IV
›Reveal solutionSolution
Biofertilizers reducing chemical fertilizer use, Rhizobium in legumes, and Glomus forming mycorrhiza are all correct; the claim that mycorrhizae "enhance phosphorus content in the soil" misstates the actual mechanism (mycorrhizal fungi absorb existing soil phosphorus and transfer it to the plant, enhancing the plant's uptake, not the soil's phosphorus content).
Concept and Intuition
Biofertilizers are living organisms that enrich the nutrient quality of soil or improve plant nutrient uptake, reducing the need for chemical fertilizers. Two textbook examples anchor this topic: Rhizobium, a symbiotic nitrogen-fixing bacterium living in legume root nodules, and mycorrhiza, a fungus–root association (classically formed by the genus Glomus) that improves the plant's phosphorus absorption by extending the effective root-surface area via fungal hyphae into the soil — the fungus draws phosphorus already present in the soil and delivers it to the plant, it does not create or add phosphorus to the soil itself.
Step-by-Step Solution
- Statement I: use of biofertilizers is specifically promoted because it reduces our dependence on chemical fertilizers — TRUE, a standard textbook statement.
- Statement II: mycorrhizal fungi absorb phosphorus that is already present in the soil and transfer it to the plant, improving the plant's phosphorus nutrition — saying they "enhance phosphorous content in the soil" mischaracterises this as increasing soil phosphorus itself, rather than the plant's uptake of existing soil phosphorus — this precise wording is INCORRECT. …
- AP EAPCET 2025Set ap-2025-05-20-FN1 markMCQQ.Choose the incorrect statement among the following (A) Super Microbes are resistant to many drugs. (B) Severe Acute Respiratory syndrome is a recently emerged disease. (C) Cyanobacteria symbiotically associated wih paddy fields as biofertiliser. (D) Nucleo polyhedrovirus are species specific insecticide.
›Reveal solutionSolution
This is a "spot the incorrect statement" question from the Microbes-in-Human-Welfare chapter; three statements are verbatim textbook facts and one quietly swaps "free-living" for "symbiotic."
Concept and Intuition
Cyanobacteria (blue-green algae) contribute to soil fertility in two genuinely different ways that examiners like to blur together:
- Free-living cyanobacteria (Anabaena, Nostoc, Oscillatoria, Aulosira) grow directly in the flooded water of paddy fields, fix atmospheric nitrogen, and add organic matter — this is what makes them valuable biofertilisers, but it is not a symbiosis; they are independent organisms, not partnered with the rice plant.
- The genuinely symbiotic nitrogen-fixing system used in rice cultivation is the Azolla–Anabaena azollae association, where the cyanobacterium lives inside cavities of the water fern Azolla.
So "cyanobacteria symbiotically associated with paddy fields" conflates the free-living biofertiliser role with the Azolla symbiosis — a factual slip.
Step-by-Step Solution
- (A) Super microbes / superbugs being multi-drug resistant — this is a standard, accepted fact about antibiotic-resistant pathogens (e.g., MRSA). True.
- (B) SARS is listed among recently emerged infectious diseases in the same chapter's discussion of emerging pathogens. True.
- (C) Cyanobacteria act as paddy-field biofertilisers, but as free-living organisms, not symbiotically. Calling this association "symbiotic" is incorrect. False — this is the answer. …
- AP EAPCET 2024Set ap-2024-05-16-AN1 markMCQQ.Assertion (A) : Biological control developed for treatment of plant diseases Reason (R) : Trichoderma are free living fungi common in root ecosystem (A) A and R are correct. R is the correct explanation of A (B) A and R are correct. R is not the correct explanation of A (C) A is correct but R is incorrect (D) A is incorrect but R is correct
›Reveal solutionSolution
Trichoderma's natural abundance as a free-living fungus in the root ecosystem is exactly why it has been successfully developed as a biological control agent against plant diseases.
Concept and Intuition
Biological control uses living organisms (rather than chemical pesticides/fungicides) to manage pests and pathogens, offering an environmentally friendlier alternative. Trichoderma species are free-living fungi that naturally colonise the rhizosphere (the root-associated soil ecosystem) of many plants. Because they are already well-adapted to compete and interact within this niche, they can outcompete, parasitize, or otherwise antagonise soil-borne pathogenic fungi (such as Fusarium wilt-causing species) that would otherwise infect plant roots; this natural root-ecosystem presence is precisely the property that biotechnologists have harnessed to develop Trichoderma-based biocontrol products.
Step-by-Step Solution
- Assertion: biological control has been developed for plant disease treatment - true, well documented (e.g., Trichoderma-based biofungicides).
- Reason: Trichoderma are free-living fungi common in the root ecosystem - true, a well-established ecological fact. …
- AP EAPCET 2024Set ap-2024-05-16-FN1 markMCQQ.The correct sequence of plants which help in production of biofertilizers, medicines and protein food. (A) Belladona, Aloe, Withania (B) Nostoc, Datura, Chlorella (C) Chlorella, Datura, Nostoc (D) Nostoc, Anabaena, Rhizobium
›Reveal solutionSolution
The three named plants/organisms must be sequenced to match "biofertilizer, medicine, protein food" — Nostoc (N-fixing biofertilizer), Datura (medicinal plant), Chlorella (protein-food alga) fits that order exactly.
Concept and Intuition
Different plants/microbes are economically important for different reasons — biofertilizers restore soil fertility via nitrogen fixation, medicinal plants supply pharmacologically active compounds, and protein-rich algae are used as food/nutritional supplements (single-cell protein).
Step-by-Step Solution
- Biofertilizer: Nostoc, a nitrogen-fixing cyanobacterium (blue-green alga), enriches soil nitrogen content — classic biofertilizer.
- Medicine: Datura is a well-documented source of tropane alkaloids used medicinally (e.g., for asthma/respiratory ailments in traditional medicine).
- Protein food: Chlorella, a unicellular green alga, is cultivated and used as a protein-rich food/dietary supplement (single-cell protein source). …
- AP EAPCET 2024Set ap-2024-05-17-AN1 markMCQQ.Choose correct pairs from the following I. Glomus - Mycorrhiza II. Blue green algae - Don't added organic matter to soil III. Azospirillum - Symbiotic organism IV. Oscillatoria - Fix atmospheric nitrogen (A) II, IV (B) I, III (C) I, IV (D) II, III
›Reveal solutionSolution
Of the four statements, only Glomus–Mycorrhiza and Oscillatoria–nitrogen fixation are factually correct pairings; the blue-green-algae and Azospirillum statements are both false.
Concept and Intuition
Biofertilizers work through different mechanisms: mycorrhizal fungi (like Glomus) form symbiotic associations with roots to improve nutrient/water uptake; free-living nitrogen-fixing bacteria (like Azospirillum, Azotobacter) fix nitrogen without a host; and nitrogen-fixing cyanobacteria (like Nostoc, Anabaena, Oscillatoria) both fix atmospheric nitrogen and add organic matter to soil upon their death.
Step-by-Step Solution
- I. Glomus – Mycorrhiza: Glomus forms arbuscular mycorrhizal (AM) associations with plant roots — this pairing is correct.
- II. Blue-green algae – Don't add organic matter: cyanobacteria are well known to increase soil organic matter content (in addition to fixing nitrogen) — this pairing is incorrect.
- III. Azospirillum – Symbiotic organism: Azospirillum is a free-living (non-symbiotic) nitrogen-fixing bacterium found in the root zone — this pairing is incorrect. …
- AP EAPCET 2024Set ap-2024-05-17-AN1 markMCQQ.Assertion (A): Bacillo viruses attack insects and arthropods Reason (R): They have no negative impact on non target insects (A) A and R are Correct and R is the Correct explanation of A (B) A and R are Correct and R is not the Correct explanation of A (C) A is Correct but R is incorrect (D) A is incorrect but R is correct
›Reveal solutionSolution
Both statements about baculoviruses are true, but the Reason (safety for non-target insects) is a separate fact about their desirability as biopesticides — it does not explain why baculoviruses attack insects and arthropods in the first place.
Concept and Intuition
Baculoviruses (occurring in the genus Nucleopolyhedrovirus) are used as species-specific, narrow-spectrum biological insecticides. Two distinct facts are usually taught about them: (1) they naturally infect insects and arthropods, and (2) because of their narrow host range, they cause no harm to non-target species, plants, or vertebrates. Fact (2) is a consequence of their host specificity, not a cause/explanation of fact (1).
Step-by-Step Solution
- Assess A: baculoviruses do attack insects and arthropods — true.
- Assess R: baculoviruses indeed have no adverse impact on non-target insects (this underlies their appeal as eco-friendly biopesticides) — true. …
- AP EAPCET 2024Set ap-2024-05-17-FN1 markMCQQ.Choose the correct statement related to biological control agents A. No negative impact on plants, mammals, birds or insects B. Ecologically sensitive area is being treated C. Species specific insecticidal applications D. Integrated pest management is not benefited (A) A, C, D (B) B, C, D (C) A, B, C (D) A, B, D
›Reveal solutionSolution
A, B and C are the standard textbook advantages of biological pest control; D is false because biocontrol is a pillar of, not a hindrance to, Integrated Pest Management. Answer: (C).
Concept and Intuition
Biological control agents (predators, parasitoids, pathogens like Bt) are valued precisely because they act selectively:
- They target the pest specifically, without collateral harm to other plants, mammals, birds, or non-target insects.
- Because they don't introduce toxic chemical residues, they are safe to deploy even in ecologically sensitive habitats.
- Their species-specific insecticidal action means only the intended pest population is affected. All of this is exactly why biological control is a cornerstone, not an excluded element, of Integrated Pest Management (IPM) programmes — so a statement claiming IPM 'is not benefited' by biocontrol is factually backwards.
Step-by-Step Solution
- Statement A: no negative impact on non-target organisms — a genuine, well-documented advantage of biocontrol. TRUE.
- Statement B: usable in ecologically sensitive areas — true, since biocontrol avoids the chemical damage pesticides would cause there. TRUE. …
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